88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



8. Cephalic fan with 39-42 branches, the pectinate hairs on these simple, very fine, 

 and close together, except at the extreme tips of the branches where they are 

 somewhat more separated ; lateral margin of submentum with 4 teeth con- 

 tiguous to each other, another small isolated one closer to the base, and 2 

 heavily-sclerotized, well-pigmented ones just posterior to apical teeth (7 in 



all) veracnisanum Vargas, Martinez, and Diaz 



Cephalic fan with 45-49 branches, the pectinate hairs on these branches bifid, 

 stout, greatly separated, with no simple, finer hairs between ; lateral margin 

 of submentum with 7 teeth, rather evenly spaced, none more heavily sclero- 

 tized or pigmented than the other colvini Dalmat 



SPECIES OF THE SUBGENUS SIMULIUM, BASED ON LARVAL CHARACTERS 



1. Rectal scales present 2 



Rectal scales absent 3 



2. Cephalic fan with 36-38 branches, these having well-developed hairs along 



their ventral margin; pseudopod with 16-20 rows of hooks; posterior sucker 

 with 66-70 rows of hooks ; submentum with apical teeth well developed and 

 with 3-4 toothlike extensions along each lateral margin. .mctalHcwn Bellardi 

 Cephalic fan with 28 branches, the hairs along their ventral margin minute; 

 pseudopod with 30-32 rows of hooks ; posterior sucker with 82-84 rows of 

 hooks ; submentum with apical teeth not as sharply defined and usually with 

 7 toothlike extensions along each lateral margin. 



jobbinsi Vargas, Martinez, and Diaz 



3. Cephalic fan with fewer than 40 branches 4 



Cephalic fan with more than 40 branches 6 



4. First two antennal segments with well-defined transverse striations; ventral 



tubercles lacking on eighth segment; ventrolateral row of submentum with 



6-10 hairs ; apical teeth of submentum broad and sharp-pointed 5 



First two antennal segments without transverse striations ; ventral tubercles 

 present on eighth segment; ventrolateral row of submentum composed of 

 4-5 hairs ; apical teeth of submentum rather slender and blunt. 



ochraceum Walker 



5. Epicranial plates with dark markings anterior to the eye spots ; occipital cleft 



with posteriorly directed prolongation at its apex; posterior sucker with 

 78-82 rows of hooks ; inner margin of anterior arms of X-shaped sclerite 



with darkened band kompi Dalmat 



Epicranial plates without dark markings anterior to eye spots ; occipital cleft 

 with rounded apex ; without prolongation ; posterior sucker with 86-94 rows 

 of hooks ; inner margin of anterior arms of X-shaped sclerite without 

 darkened band tricornis De Leon 



6. Anal gills with 14-18 branches; posterior sucker with 84-86 rows of hooks; 



ventrolateral row of submentum with 7 hairs ; cephalic fan with 46-48 



branches parrai Vargas, Martinez, and Diaz 



Anal gills with 3 simple trunks, or each of these subdivided into 3 to give a 

 maximum of 9 branches in all ; ventrolateral row of submentum composed of 

 4-5 hairs; cephalic fan with 58-64 branches. . . .jacumbae Dyar and Shannon 



